Epoxy-polish fiber optic connectors have been used in fiber communications systems for a number of years. These connectors are used to terminate the ends of optical cables so that the cables can be appropriately connected to various types of fiber optic equipment, and other such fiber optic cables. There are a variety of connector styles in use, with each style suited to a specific business or application segment. Although some connectors are installed on the ends of fiber optic cables in the field when the cables are installed in a system, most high-quality connector terminations are installed in a factory environment where specially configured production equipment can be used to create a uniformly consistent, high quality product.
Typically, a connector on a fiber optic cable is made up of several discrete components, including: 1) a plastic, metal, or ceramic ferrule to support the small, 125 μm glass optical fiber accurately in place; 2) a housing to support the ferrule and to introduce a mechanism to connect to another connector or device; 3) a spring to allow movement of the ferrule to connect to another connector; 4) a crimp band that secures a strength member (made of Kevlar, or the like) to the connector to provide strain relief; and 5) a boot to allow for cable flexing near the back of the unit. In a typical manufacturing operation for optical connectors, several production steps are performed in succession, and much of this has been done manually. First, a cable is stripped of its outer layer or layers down to the layer close to and containing the delicate glass optical fiber. These layers are typically as follows: a glass fiber (125 μm diameter with a 250 μm coating), a buffer layer (600-900 μm), a layer of aramid yarn (strength member), and the outer jacket (1.6-3.0 mm). Each layer is cut to a specific length to support a given connector style properly. Hand tools, strippers, and cutters have been used for this operation, along with some automated pneumatic and electrical devices. A small amount of epoxy is then injected into the ferrule through a small hole, and the optical fiber is fed through the epoxy-filled ferrule. The optical fiber fed through the connector ferrule is longer than ultimately needed, so that it extends well beyond the ferrule. This excess length of fiber is subsequently removed. By using more glass fiber than needed, it is ensured that the glass fiber does not terminate below the surface of the connector ferrule.
Next, the connector is exposed to an elevated temperature in an oven to cure the epoxy and to secure the fiber in place permanently. Typically, a single connector is manually placed in an oven by itself, and then removed and allowed to cool. After the epoxy is cured and the connector cooled, the excess glass fiber protruding from the end of the connector ferrule is removed. A hard blade or tip, such as a diamond, ruby, or carbide device, is used to score the fiber close to the ferrule end face, producing a clean fracture line in the glass. The excess fiber is then manually removed and discarded. The end of the glass fiber is then buffed, and the fiber and the ferrule end face are polished. A problem sometimes arises in accurately scoring the glass so that a clean fracture can be achieved, since the position and size of the score line is smaller than can be observed by the naked eye. A poor cleave or break can cause a fracture that leaves part or all of the glass fiber below the end surface of the ferrule. In many cases, the glass left below the flush surface of the ferrule end face cannot be reached during polishing, thus preventing adequate optical performance from being achieved by the connector. To compensate for this, more glass fiber is left protruding from the ferrule. A lightly abrasive film or pad can then be used to polish the glass and epoxy down manually, bringing the end of the glass and encapsulating epoxy bead to the surface or close to the surface of the ferrule end face. This, of course, requires an additional step, adding to cost. An alternative method is to use a laser to burn the glass off at the end of the ferrule. Though this is an effective method, the equipment is expensive, and the process requires additional safety precautions.
After the buffing process, the connectors are then typically loaded into a fixture and polished by machine with various lapping films to produce a well-shaped connector tip with a mirror-like surface having almost no imperfections. Since there are many variations in the types of connectors, cables, and individual processes involved in the manufacture of optical cable assemblies, it has been difficult to effect improvements that are effective in dealing with such a variety of connectors.